173 research outputs found
Introduction of the composite materials and applications for manufacturing technology
A composite material can be defined as a combination of two materials resulting in better properties than those of the individual's compound used. The two constituents form a matrix and reinforcement. the main advantages of composite materials are their high strength and rigidity, combined with low density compared with bulk materials, which allows a reduction in weight in the finished part..
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Occupancy monitoring and prediction in ambient intelligent environment
Occupancy monitoring and prediction as an influential factor in the extraction of occupants' behavioural patterns for the realisation of ambient intelligent environments is addressed in this research. The proposed occupancy monitoring technique uses occupancy detection sensors with unobtrusive features to monitor occupancy in the environment. Initially the occupancy detection is conducted for a purely single-occupant environment. Then, it is extended to the multipleoccupant environment and associated problems are investigated. Along with the occupancy monitoring, it is aimed to supply prediction techniques with a suitable occupancy signal as the input which can enhance efforts in developing ambient intelligent environments. By predicting the occupancy pattern of monitored occupants, safety, security, the convenience of occupants, and energy saving can be improved. Elderly care and supporting people with health problems like dementia and Alzheimer disease are amongst the applications of such an environment. In the research, environments are considered in different scenarios based on the complexity of the problem including single-occupant and multiple-occupant scenarios. Using simple sensory devices instead of visual equipment without any impact on privacy and her/his normal daily activity, an occupant is monitored in a living or working environment in the single-occupant scenario. ZigBee wireless communication technology is used to collect signals from sensory devices such as motion detection sensors and door contact sensors. All these technologies together including sensors, wireless communication, and tagging are integrated as a wireless sensory agent
Digital Beamforming Techniques for Passive UHF RFID Tag Localization
Radio-frequency identification (RFID) technology is on the way to substitute traditional
bar codes in many fields of application. Especially the availability of passive ultra-high
frequency (UHF) RFID transponders (or tags) in the frequency band between 860 MHz
and 960 MHz has fostered the global application in supply chain management. However,
the full potential of these systems will only be exploited if the identification of objects
is complemented by accurate and robust localization.
Passive UHF RFID tags are cost-effective, very small, extremely lightweight, maintenancefree,
rugged and can be produced as adhesive labels that can be attached to almost any
object. Worldwide standards and frequency regulations have been established and a
wide infrastructure of identification systems is operated today. However, the passive
nature of the technology requires a simple communication protocol which results in
two major limitations with respect to its use for localization purposes: the small signal
bandwidth and the small allocated frequency bandwidth. In the presence of multipath
reflections, these limitations reduce the achievable localization accuracy and reliability.
Thus, new methods have to be found to realize passive UHF RFID localization systems
which provide sufficient performance in typical multipath situations.
In this thesis, an enhanced transmission channel model for passive UHF RFID localization
systems has been proposed which allows an accurate estimation of the channel
behaviour to multipath. It has been used to design a novel simulation environment and
to identify three solutions to minimize multipath interference: a) by varying the channel
interface parameters, b) by applying diversity techniques, c) by installation of UHF
absorbers. Based on the enhanced channel model, a new method for tag readability
prediction with high reliability has been introduced. Furthermore, a novel way to rate
the magnitude of multipath interference has been proposed. A digital receiver beamforming
localization method has been presented which uses the Root MUSIC algorithm
for angulation of a target tag and multipath reducing techniques for an optimum localization
performance. A new multiangulation algorithm has been proposed to enable
the application of diversity techniques. A novel transmitter beamforming localization
approach has been presented which exploits the precisely defined response threshold
of passive tags in order to achieve high robustness against multipath. The basic technique
has been improved significantly with respect to angular accuracy and processing
times. Novel experimental testbeds for receiver and transmitter beamforming have been
designed, built and used for verification of the localization performance in real-world
measurements. All the improvements achieved contribute to an enhancement of the accuracy and especially
the robustness of passive UHF RFID localization systems in multipath environments
which is the main focus of this researc
A study of RF-over-fibre based active RFID indoor location system
Location systems developed for indoor environments have attracted increasing
interest, as a result of the rapidly growing location and navigation services provided
by the Global Positioning System (GPS). Location information of people and objects
can be used to cooperate with existing communication or database systems to provide
abundant services to system operators and end users. For example, equipment tracking
in hospitals ensure that location of the appropriate equipment can be provided
simultaneously with necessary medical services; attendee tracking at conferences may
encourage more efficient communications and networking; location of valuable assets
in factories or warehouses aids logistics and protects these assets from theft. Since
established global and terrestrial navigation systems cannot provide reliable location
services in indoor environments, these demands are increasingly being met by
wireless indoor location systems.
A review of the existing systems reveals that the current systems are able to provide
either an accurate location service with sophisticated system design at higher cost or a
less accurate location service by means of integrated systems supplemented by
existing facilities.
This thesis presents a novel design of an indoor location system that is based on an
RF-over-fibre backbone network, which is able to provide high location accuracy
while the network infrastructure can be shared with multiple wireless systems. It is the
first such demonstrator in this area. This research has been conducted by the author
through a research project called The Intelligent Airport (TINA), which is the
motivation for this research.
The TINA project seeks to develop a new seamless wireless/wired ubiquitous
infrastructure with high levels of computational capability to meet the application
requirements of future airport environments. In the TINA system, multiple wireless
services are provided through an integrated system supported by an RF-over-Fibre
network, which transports RF signals through optical fibres. The active RFID indoor location unit is an essential part of the TINA system, which will facilitate the
infrastructure to provide location-based services.
The thesis describes the detailed design of the active RFID indoor location system
proposed for the TINA project, and a few key issues discovered during trials of the
demonstration system developed. The overall system design, including ranging
technique, TDOA location finding algorithm, and hardware implementation, is
presented in this thesis. Particular contributions also include a numerical algorithm for
solving target location from TDOA measurement and a technique to determine the
chirp linearity requirement. The field trial results of the system design demonstrate the
principals and their location performance. The system has the potential to be extended
to other scenarios where RF-over-fibre networks are employed and accurate location
ability is desired
A State-of-the-Art Survey of Indoor Positioning and Navigation Systems and Technologies
The research and use of positioning and navigation technologies outdoors has seen a steady and exponential growth. Based on this success, there have been attempts to implement these technologies indoors, leading to numerous studies. Most of the algorithms, techniques and technologies used have been implemented outdoors. However, how they fare indoors is different altogether. Thus, several technologies have been proposed and implemented to improve positioning and navigation indoors. Among them are Infrared (IR), Ultrasound, Audible Sound, Magnetic, Optical and Vision, Radio Frequency (RF), Visible Light, Pedestrian Dead Reckoning (PDR)/Inertial Navigation System (INS) and Hybrid. The RF technologies include Bluetooth, Ultra-wideband (UWB), Wireless Sensor Network (WSN), Wireless Local Area Network (WLAN), Radio-Frequency Identification (RFID) and Near Field Communication (NFC). In addition, positioning techniques applied in indoor positioning systems include the signal properties and positioning algorithms. The prevalent signal properties are Angle of Arrival (AOA), Time of Arrival (TOA), Time Difference of Arrival (TDOA) and Received Signal Strength Indication (RSSI), while the positioning algorithms are Triangulation, Trilateration, Proximity and Scene Analysis/ Fingerprinting. This paper presents a state-of-the-art survey of indoor positioning and navigation systems and technologies, and their use in various scenarios. It analyses distinct positioning technology metrics such as accuracy, complexity, cost, privacy, scalability and usability. This paper has profound implications for future studies of positioning and navigation
Angle of Arrival Estimation Utilising Frequency Diverse Radio Antenna Arrays
The purpose of this research is to investigate a novel way of combining carrier signals that are transmitted successively over Multiple Frequencies (MF) and traditional metrics to improve AoA estimation. Every signal contains three metrics, amplitude, phase, and frequency. To achieve localisation, current systems utilise the metrics of amplitude (also known as Received Signal Strength (RSS)) and phase that resolves the AoA. However, the metric of frequency is mostly used with Orthogonal Frequency-Division Multiplexing (OFDM) to increase the number of RSS and AoA metrics, which is not optimal.
This research answers two questions. Can the use of MF improve AoA estimation? Also, how can MF and traditional metrics be combined for AoA estimation? The aim is to prove that the metric of frequency can be utilised more optimally. Therefore, measurements of RSS and AoA are performed in different environments for MF. To perform these measurements, ten frequency diverse Software Defined Radios (SDRs) are employed. A novel technique to time/frequency synchronise the SDRs is developed and presented. Moreover, a ten element Uniform Linear Array (ULA) is designed, simulated and manufactured. The outcomes of this research are two novel algorithms for the MF AoA estimation of a carrier transmitter.
Findings of the first algorithm show that the use of MF with the RSS metric performs equally with current systems that have a higher cost and complexity. The second algorithm that utilises MF with the AoA metric demonstrates a significant reduction in the AoA estimation error, compared to current systems. Specifically, for 50\% of the measured cases the AoA estimation error is reduced by 3.7 degrees, while for 95\% of the measured cases the AoA estimation error is reduced by 27 degrees. Hence, this research proves that MF with traditional metrics can reduce system complexity and greatly improve AoA estimation
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